The invention relates to a honeycomb structure made of a non-woven which can be produced from recycled carbon fibers.
Carbon fibers are used in a wide variety of products, for example in sports equipment and vehicles, and in products which can exhibit usefulness and artistic design. They are mostly used after embedding within a plastics matrix, the term used here being carbon-fiber-reinforced plastics, abbreviated to CFRP.
In view of increasing use of carbon fibers in consumer products, and also in vehicles, recycling of wastes comprising carbon fibers is an increasingly important challenge. It is not usually possible to apply molding processes to used parts made of CFRP, because the matrices surrounding the carbon fibers are mostly thermosets.
Carbon non-woven is used to dissipate static charges and to provide electrical conductivity. It is composed of short carbon filaments randomly mutually superposed under pressure, and is by way of example obtainable in the form of rolls of width 1 m.
Carbon-fiber non-wovens made of recycled carbon fibers are by way of example known from the document WO 2013/144844 A1.
Honeycomb structures are known as core material for sandwich structures. They are used in a wide variety of applications, for example in surfboards and spacecraft. The document EP 1515835 B1 thus describes a process for the production of a carbon honeycomb body by using a resin-impregnated honeycomb base structure made of paper or non-woven. The paper or nonwoven here is first pyrolysed and compacted/stabilized; the stabilized honeycomb is coated with a carbon-containing solution, and then again pyrolysed.
The document EP 0113841 B1 relates to a process for the production of a molding made of composite material by applying synthetic-resin-impregnated laminate layers onto a male mold, where, during the build-up of the layers, a multiple/double layer composed of two or more cellular core layers or honeycomb layers is introduced into the neutral zone of the aforementioned layers, and the multiple or double layer is produced as unit and is inserted as unit between the laminate layers, where a self-supporting, load-bearing bonding layer made of woven glass fabric, carbon-fiber non-woven, polyamide or the like, or of synthetic-resin-impregnated non-woven or woven fabric is arranged between each two cellular core layers or honeycomb layers.
Resin-impregnated papers made of aromatic polyamides have moreover been disclosed, as also have production processes for honeycomb cores, and honeycomb cores made of woven CFRP fabrics of the type that can by way of example be produced manually for spacecraft.
However, the prior art comprised no relatively low-cost sandwich-core structures which take the form of honeycombs and permit effective introduction of tangential shear forces from the outer layers via the honeycomb structure into the respective opposite outer layer.